In one aspect, the present invention relates to coating processes, such as dip coating processes, for coating the surfaces of long, cylindrical or tubular materials. In particular, the invention relates to dip coating processes and apparatuses for coating the external surfaces of medical materials such as catheters and guidewires.
Many medical devices, particularly those implanted in the body on either a permanent, temporary or transient bases, are often provided with surface coatings intended to achieve a particular purpose, such as improved lubricity, biocompatibily, hemostasis, or the like.
Conventional applications of such dip coating techniques are described, for instance, in U.S. Pat. Nos. 5,429,618; 5,443,453; 5,464,650; 5,541,167; 5,531,715; 5,538,512; 5,603,991 and 5,702,823, the disclosures of each of which are incorporated herein by reference.
Dip coating has long been used as a common coating technique, and its applicability to medical devices is well established. See, for instance, xe2x80x9cCoating Application and Curing Techniquesxe2x80x9d, Chapter 6 in Hydrophilic Polymer Coatings for Medical Devices, Catheters, R. J. LaPorte, ed. (1997), which describes the advantages associated with this method as including lower equipment costs, and complete, uniform, application of the coating to the device. Disadvantages, however, may include the need for relatively large volumes of coating fluid.
The above advantages are most apparent, however, in situations where either the entire device (such as a catheter or guidewire), or even a discrete terminal portion thereof, is to be coated. In such cases, it is quite easy to dip the entire device, or the distal portion, into the necessary solution(s). A further, and particular, disadvantage of dip coating techniques, however, arises in the situation where it is necessary to coat only intermediate and/or discontinuous portions of the device. Often, for instance, both distal ends of a device are not to be coated (e.g., in the event they provide a different structural feature or function than the intermediate portion(s)).
Intermediate and discontinuous coatings are typically provided in one of two waysxe2x80x94either by somehow masking the areas not to be coated, in order to prevent them from contacting the coating solution, or by simply not permitting coatings in certain areas to become effectively bound thereto (e.g., shielding them from the application of curing radiation, and the like).
Such approaches, however, are themselves cumbersome, and can be particularly wasteful of coating reagents. Typically, for instance, the entire masking material, once coated with the coating material, will simply be discarded if not reused. Clearly new and improved methods and apparatuses for coating intermediate would provide a variety of advantages.